The only way to open a .tax file from 2004 is with the TurboTax software for 2004. The software is no longer available. If you don't have a working copy, you could try TaxPrinter. You send them your .tax file and they send you back a PDF of the tax return, which you can then print with Acrobat Reader.
TaxPrinter has no connection with TurboTax. I have never used TaxPrinter, so I cannot make a recommendation. I'm just making you aware of it.
TT no longer offers software to open the file. I'm not even sure that 2004 software could run on modern day computers. any you find offered on the web and use to open the return could change it since those can not be updated. there are some online services that say they can print old tax files, but I am not sure that I would ever send my identity and tax information to some unknown website. did you keep a pdf of the file? even the IRS doesn't maintain transcripts going back that far.